Vapor phase corrosion inhibition



United States Patent 3,433,577 VAPOR PHASE CORROSION INHIBITION PhilipE. Shick, Toledo, Ohio, assignor to Owens-Illinois, Inc., a corporationof Ohio No Drawing. Filed Aug. 19, 1964, Ser. No. 391,077 US. Cl. 2l2.59 Claims int. Cl. 865d 85/00; C23f 15/00 ABSTRACT OF THE DISCLOSURE Amethod of protecting metal articles of manufacture from atmosphericcorrosion which comprises packaging the articles in a packaging materialwhich has been treated with a vapor phase corrosion inhibitorcomposition consisting essentially of sodium nitrite and sodiumphosphate.

The present invention relates to improvements in vapor phase corrosioninhibition and more particularly, to vapor phase corrosion inhibitingcompositions for use in connection with packaging metal articles whichare subject to attack by corrosive forces and for methods of using same.The present invention also relates to packaging materials having appliedthereto the vapor phase corrosion inhibitor compositions referred toabove.

Corrosion and its causes have been the subject of much study in previousyears. It is known, for example, that iron rusts in the atmospherebecause of a chemical interaction that takes place between the iron, andthe moisture and oxygen in the air. Since it is difficult and extremelyimpractical to remove oxygen from the atmosphere in which metal articlesare packaged, corrosion is often a problem during the storage, handlingand transportation of objects formed of a corrodible material. Previousmethods have been developed to combat this corrosion such as applying acoating on the surfaces of corrodible materials. As can be appreciated,such methods are cumbersome and require excessive amounts of labor andtime to apply the coatings and often cannot adequately or completelycover the surfaces in order to protect the metal article. For example,oil and grease coatings have been applied directly to the metalsurfaces, and waterproof wraps or packages have also been employed.However, because of hte aforementioned difliculties these methods havenot been entirely satisfactory.

A highly successful system of preventing the corrosion of packaged metalarticles has been developed in recent years known as vapor phasecorrosion inhibition. This method functions to prevent corrosion ofmetal objects by the moisture and oxygen present in the atmosphere incontact with the metal articles. By obviating the necessity of removingthe moisture and oxygen from the atmosphere surrounding the packagedmaterials, or directly coating the metal surfaces with a protectivecoating, the vapor phase corrosion inhibitors represent an extremelypractical, economical and advantageous solution to the problem ofpreventing corrosion. Functioning by slowing releasing vapors thatcontact the surfaces of the metals, the vapor phase corrosion inhibitorsserve to envelope the metal articles in a non-corrosive atmosphere andretard the moisture and oxygen present in the atmosphere from attackingthe metal surfaces.

Customarily, the vapor phase corrosion inhibitor compositions areapplied to paper, wrapping materials, liners, and sheets for corrugatedboxes or other inert, solid carriers employed as packaging means inwhich the metal article is packaged. Other materials such as wood fibersand chips, and other porous packaging materials can be utilized in asimilar manner. One advantage of this system of protecting metalarticles from corrosion resides p CC in the fact that it is notnecessary to apply or coat the compounds themselves onto all of thesurfaces of the metal articles so wrapped in order to obtain effectiveprotection. The vapor phase corrosion inhibitor composition volatilizesextremely slowly to release agents into the atmosphere which effectivelypermeate the air surrounding the metal article within the package andthus functions to prevent corrosion. However, prior known vapor phasecorrosion inhibition methods and compositions have had associatedtherewith certain drawbacks and disadvantages. For example, certaincompounds previously used for this purpose were lacking in effectivenessand others were too costly for packaging low cost items.

It is accordingly an object of the present invention to provide improvedvapor phase corrosion inhibition of metal articles which avoids thedisadvantages of prior methods and compositions.

It is a further object of the present invention to provide -a method forprotecting metal articles by vapor phase corrosion inhibition thateliminates the difiiculties of prior known methods.

It is a further object of the present invention to provide a compositionfor vapor phase corrosion inhibition that is relatively inexpensive andit is particularly effective in reducing the corrosive action ofmoisture and air on metal articles of manufacture.

It is a further object of the present invention to provide -a packagingmaterial that will inhibit corrosion of metallic articles in theimmediate vicinity thereof.

In obtaining the above objects, one feature of the present inventionresides in a method for protecting metal articles of manufacture fromatmosphere corrosion caused by moisture and air by having present in theimmediate vicinity of the metal articles sodium nitrite as a vapor phasecorrosion inhibitor.

Another feature of the present invention resides in a vapor phasecorrosion inhibitor composition consisting essentially of sodium nitriteand sodium phosphate.

Another feature of the present invention resides in a packaging materialimpregnated with sodium nitrite as a vapor phase corrosion inhibitor.

The above and other objects, features and advantages of the presentinvention will become apparent from the following detailed descriptionthereof.

According to the present invention a composition consisting essentiallyof sodium nitrite and sodium phosphate has been found to be particularlyvaluable for purposes of vapor phase corrosion inhibition. Brieflydescribed, the invention is carried out by applying a solution of sodiumnitrite and sodium phosphate to the packaging material used forpackaging metal articles of manufacture. Heretofore, both sodium nitriteand sodium phosphate have been considered to be essentially non-volatileand, therefore, presumed to be ineffective for purposes of vapor phasecorrosion inhibition.

Although consisting essentially of sodium nitrite and sodium phosphate,the vapor phase corrosion inhibitor composition of the present inventionmay contain minor amounts of other ingredients that do not adverselyalfect the effectiveness of the compositions. The composition can beapplied in the form of a solution, dispersion, paste and the like towrapping materials such as paper, cardboard, fiber-board, wood, fabrics,fibers, inorganic and organic wrapping and packaging materials in anyshape or form by coating, impregnating or any other manner ofapplication.

The present invention is particularly effective when the relativeproportions of the materials are in the ratio of 3 parts of sodiumnitrite to 1 part of sodium tribasic phosphate. It is to be understood,however, that the proportions can range from about 5% to sodiumphosphate, the remainder being sodium nitrite.

Any suitable solvent can be employed for mixing with the inorganic saltsto form the treating composition and water and alcohol-water mixture aregenerally preferred.

The following examples are illustrative but not limiting of the presentinvention.

EXAMPLE I An essentially saturated solution containing approximately 3parts of sodium nitrite and 1 part of sodium phosphate was applied to asingle face liner of a corrugated board to give a total addition ofapproximately 2 lbs. of solid per 1000 square feet of board. Thesolution completely impregnated the surface of the board and imparted abrownish color in appearance compared to the untreated kraft paper. Theboard was thereafter dried by use of a pre-heater. The treated board wasthen fabricated into corrugated boxes which may be used without furthertreatment for the packaging of metallic articles which are susceptibleto attack by corrosive forces in the atmosphere.

EXAMPLE II This test was conducted to determine and compare theeffectiveness of the vapor phase corrosion inhibitor composition of thepresent invention with various prior known materials.

In these tests the metal cans employed were No. 303 cans of Del Montecorn. The cans were packed one dozen to a box and 2 boxes were used totest each coating material.

Prior to the tests the cans were individually inspected for rust and thelabels were slit and fastened with rubber bands to permit easyinspection. Moreover, the metal surfaces of several cans in each boxwere scratched, both on the lids and under the labels in order to inducerusting.

The average test cycle consisted of a 6 hr. period exposed to standardconditions, namely 73 F. at 50% relative humidity followed by a 2 hr.period under cold room conditions at F., followed by a 16 hr. period at90 F. and 85% relative humidity. The test was carried through ninecycles without the cold room conditions and four cycles with cold roomconditions.

The over-all average based on the test cycle including the cold roomconditions was determined at the termination of the test shown in thetable below. Coatings which provided the best protection are first onthe list. Others are in the order of decreasing protection. The scale ofgrading ran from A to D with A indicating no rust and D indicatingsevere rust patches.

TABLE 1.RESULTS OF CAN TEST In the above table, the Blank coatingrepresents those cans which were packaged in containers which did nothave any treatment. The test results clearly show that the vapor phaseinhibitor composition of the present invention is superior to othercoatings.

The proportions of the inhibiting composition adding to the packagingmaterial can vary over a considerable range as for example, 1.2 lbs. toabout 3 lbs. per thousand sq. ft. of packaging material, although morecan also be used. Generally at least about 0.5 lb. per thousand sq. ft.should be employed. The exact proportions and amounts employed is not acritical feature of this invention.

It has been ascertained that the temperature of the surroundings willaffect the performance of the vapor phase corrosion inhibitorcompositions of the present invention. Generally, tests have shown thatthe compositions of the present invention are effective over a range oftemperatures from below freezing to 95 F. and higher.

The temperature and moisture content may have an important influence onboth the stability and life of the coating composition and to thetendency of the protected item to corrode.

Although the foregoing description emphasizes the preferred embodimentof the present invention, i.e., the combination of sodium nitrite andsodium phosphate, it is understood that packaging materials such ascartons wherein the entire internal surfaces thereof are treated withsodium nitrite have been found to give sufiicient protection tocorrodible substances packaged therein to meet standard requirements. Inaddition, other alkaline inorganic salts may also be employed in placeof the sodium phosphate, such as sodium carbonate, sodium borate and thelike.

Various materials can be packaged in the treated packaging materialsproduced according to the present invention including metal containers,piping, fittings, and innumerable other items.

What is claimed is:

1. A method of protecting metal articles of manufacture from atmosphericcorrosion caused by moisture and air which comprises packaging saidmetal articles in the presence of an inert carrier having appliedthereto, in an amount effective to protect against corrosion, anon-volatile corrosion inhibitor composition consisting essentially ofsodium nitrite and sodium phosphate which forms a protective vaporatmosphere in contact with the metal articles.

2. A method of protecting metal articles of manufacture from atmosphericcorrosion caused by moisture and air which comprises packaging saidmetal articles with an inert carrier having applied thereto, in anamount effective to protect against corrosion, a non-volatile corrosioninhibitor composition consisting essentially of about 5% to about 75%sodium phosphate and about 25 to about sodium nitrite, to form aprotective vapor atmosphere in contact with the metal articles.

3. A packaging material for inhibiting corrosion of metallic articles ofmanufacture packaged therein comprising an inert, solid carrier havingapplied thereto, in a quantity effective to protect against corrosion, anonvolatile corrosion inhibitor composition consisting essentially ofsodium nitrite and sodium phosphate, to form a protective vaporatmosphere in contact with the metallic articles.

4. A packaging material for inhibiting corrosion of metallic articles ofmanufacture packaged therein comprising an inert porous solid carrierimpregnated with, in a quantity effective to protect against corrosion,a nonvolatile corrosion inhibitor composition consisting essentially ofsodium nitrite and sodium phosphate, to form a protective vaporatmosphere in contact with the metallic articles.

5. A packaging material as defined in claim 4 wherein the compositionconsists essentially of from about 5% to 75% sodium phosphate and about25% to about 95% sodium nitrite.

6. A packaging material for inhibiting corrosion of metallic articles ofmanufacture packaged therein comprising an inert porous solid carrierhaving applied thereto a non-volatile corrosion inhibitor compositionconsisting essentially of sodium nitrite and sodium phosphate, theamount of non-volatile corrosion inhibitor composi tion being at leastabout 0.5 pound per thousand square feet of packaging material and whichforms a protective vapor atmosphere in contact with the metallicarticles.

7. A vapor phase corrosion inhibiting composition for inhibitingcorrosive attack on metal articles of manufacture by elements in theatmosphere which vapor phase inhibiting composition is adapted forapplication to packaging material utilized in the packaging of the metalarticle of manufacture and which consists essentially of sodium nitriteand sodium phosphate.

8. A vapor phase corrosion inhibitor composition for inhibitingcorrosive attack on metal articles of manufac- 5 6 ture caused bymoisture and air, consisting essentially of OTHER REFERENCES about 5% toabout 75% sodium phosphate and about 25% to about 95% sodium nitrite.Speller, F. N., CorrosionCauses and Prevention.

9. In the method of making packaging material for McGraw-Hill, New York,1935, TA46757 (Scientific Liuse in packaging metal articles that aresusceptible to cor- 5 b 361, T051011 wherein the Packaging mater i211has pp Uhlig, H. H., Corrosion and Corrosion Control. Wiley thereto anon-volatile corrosion inhibiting composition & Sons New York 1963 TA462 U4 (S i ifi Lifor inhibiting corrosive attack on the metal articlespackbrary), (Rece'ived by Library in April 1963) aged therein, theimprovement which comprises impregnating said packaging material with acomposition con- 10 MORRIS O. WOLK, Primary Examiner. sistingessentially of sodium nitrite and sodium phosphate.

BARRY S. RICHMAN, Assistant Examiner.

References Cited FOREIGN PATENTS 131,971 3/1949 Australia. 15 2 2- 7; 1117-152 647,200 12/1950 Great Britain.

